The New York Times
December 8, 2011, Kirk Johnson

Chemicals used to hydraulically fracture rocks in drilling for natural gas in a remote valley in central Wyoming are the likely cause of contaminated local water supplies, federal regulators said Thursday. The draft report, after a three-year study by the Environmental Protection Agency, represents a new scientific and political skirmish line over whether fracking, as it is more commonly known, poses a threat in the dozens of places around the nation where it is now being used to extract previously unreachable energy resources locked within rock.The study, which was prompted by complaints from local residents about the smell and taste of their water, stressed that local conditions were unusual at the site, called the Pavillion field, in that the gas wells were far shallower than in many other drilling areas around the country. The shallow depth means that natural gas itself can seep upward naturally through the rock, and perhaps into aquifers. ...

http://www.nytimes.com/2011/12/09/us/epa-says-hydraulic-fracturing-likely-marred-wyoming-water.html?_r=2&ref=us